1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having plastic substrates with integral spacers that concurrently act as supporting posts, which can prevent the deterioration of pictures resulting from non-uniformity of the disposition of spacers.
2. Description of the Prior Art
As generally known in the art, a liquid crystal display device has been generally employed as a means for representing information in a communication terminal, following the development of wireless mobile communication. Further, because consumers require diverse characteristics such as a high quality of the terminal, mobility, ability to do a large amount of information processing, light-weight, and ability to prevent breakage occurring by being dropped during use, various technologies have been developed to satisfy such requirements. For example, glass materials have been substituted with plastic materials as a substrate in order to prevent the glass substrates of a mobile terminal from being broken resulting from dropping during use.
Meanwhile, it is necessary to form a thin film transistor (TFT) on a plastic substrate in order to process large amounts of information at one time and to make the communication terminal light. For this purpose, high polymer materials such as polycarbonate, polyimide, PES (polyether sulfone), PAR, PEN (polyethelene), and PET (polyether) are employed as materials for a plastic substrate, and the heat resistant temperature limit of the polymer materials is about 150 to 200xc2x0 C.
Further, as regards a conventional liquid crystal display device employing glass substrates, response speed, contrast ratios, sight angle, luminance uniformity, etc., are closely related to the thickness of the liquid crystal layer, that is, the cell gap of the liquid crystal display device. Accordingly, spherical spacers are scattered in a space made between the substrates in order to maintain a uniform cell gap in the conventional liquid crystal display device.
As regards the scattering method for the spaces, in a dry method, spacers are electrified to result in uniform scattering of the spacers by the repulsive power of spacers with the same polarities, and in a wet method, spacers are scattered after they are mixed with solvents such as IPA, etc. Generally, the dry method above has been employed in the method for fabricating a TFT-LCD (thin film transistor liquid crystal display device), as it is comparatively better in scattering uniformity characteristics.
Accordingly, in the case of a communication terminal with mobile functions and employing plastic substrates, spacers necessarily must be scattered by the dry method or the wet method in order to maintain a uniform cell gap between substrates in the fabricating process.
However, in the case of the liquid crystal display device employing plastic substrates and in which spherical spacers are scattered, the plastic substrates can be curved or curled like paper, which phenomenon is related to the flexible characteristics of the plastic substrates. As a result, luminance non-uniformity has been produced at a specific gradation while driving a gray scale.
Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a liquid crystal display device with spacers integrally formed at plastic substrates, which can prevent luminance non-uniformity produced from drifts and conglomerations of the spherical spacers.
In order to accomplish this object, there is provided a liquid crystal display device with spacers integrally formed at plastic substrates, the liquid crystal display device comprising: upper and lower substrates joined with liquid crystals interposed there-between, at least one substrate of which is made of plastic; a driving electrode of the liquid crystals formed at the lower substrate; polarizers attached at respective rear surfaces of the upper and lower substrates; spacers interposed between the upper and lower substrates to maintain cell gaps, wherein the spacers are integrally formed at the substrate, and concurrently act as supporting posts.
Further, spacers are integrally formed at either one of the lower plastic substrate or one of the upper plastic substrate, also the spacers can be integrally formed at both of the lower plastic substrate and the upper plastic substrate.
Also, the spacers have a height of xe2x80x9ccell gapxc2x1axe2x80x9d, wherein the cell gap is 0.2 to 10 xcexcm and xe2x80x9caxe2x80x9d is not more than 1 xcexcm.
Additionally, the spacers are integrally formed with at least one plastic substrate either by a roll extrusion method employing a roll having concave patterns in the shape of the spacers or by a molding method employing mold frames having concave patterns in the shape of the spacers.